The present invention relates to a shutoff and/or control assembly for use in regulating the discharge of molten metal from a metallurgical vessel. More particularly, the present invention relates to such an assembly including a refractory ceramic rotor member to be mounted on and coupled to a stator so that the rotor member is rotatable relative to the stator to control discharge of the molten metal, and a drive rod having an outer end to be connected to and rotated by a drive unit and an inner end extending into the rotor member and coupled to and engaging therewith such that rotation of the drive rod causes rotation of the rotor member. The present invention also is directed to a novel and improved drive rod for use in such an assembly.
A shutoff and control device of this general type is disclosed in WO 88/04209 and is advantageous in that the assembly or device is constructed to enable the drive rod to tilt relative to the control rotor member. Thus, errors in alignment in the axial direction between the drive rod and the rotor member are accommodated, therefore avoiding the previous potential disadvantage of jamming during operation. Such assembly has the further advantage that the rotor member itself is not rotated by the drive unit, and therefore the rotor member is not subjected over the entire axial length thereof to a rotary torque. In total, the kinematics of this construction during operation are advantageous.
However, such known construction has certain disadvantages. Particularly, the drive rod is positioned within the shutoff and control rotor member by means of an end ball and socket-type arrangement. As a result, the rotor member is not subjected to flexural forces during drive. The rotor member can be raised and lowered by the drive rod and also can be rotated thereby. However, as a practical matter the transfer of rotation to the rotor member is complex in design and has a negative impact on the ability of the drive rod to tilt or incline relative to the rotor member.
A similar shutoff and control device is disclosed in German DE 37 43 383 A1. In this assembly, the shutoff and control rotor member only is raised or lowered by the control rod, and is not rotated thereby. However, in this arrangement also the drive rod engages with the shutoff and control rotor member by means of a ball-socket connection located deeply within the rotor member, almost to a position adjacent the outlet opening or openings in the rotor; member.
In such prior art assemblies, the drive rods are formed of metal. It has been found however that this is a disadvantageous arrangement since the molten metal located externally of the rotor member generates a very high temperature in the interior of the rotor member. As a practical matter, such a condition requires that the metal drive rod be cooled. Such cooling however is time consuming and can lead to dangerous conditions in the event of a failure of the assembly. Additionally, the metal drive rod undergoes a relatively high degree of thermal expansion, and this also is disadvantageous.